1. Field of the Invention
The present invention relates to an optical scanner configured to scan target surfaces with laser beams emitted from a plurality of light sources and deflected by a light deflector.
2. Description of Related Art
In a tandem-type image forming apparatus in which a plurality of photoconductor drums are arranged in tandem, an optical scanner is provided for exposing photoconductor drums with light. The optical scanner is configured to scan surfaces of the photoconductor drums with laser beams that are emitted from a plurality of light sources and deflected by a light deflector such as a polygon mirror.
One example of such an optical scanner, known in the art, includes a plurality of laser light sources, a light deflector configured to reflect laser beams emitted from the laser light sources so as to deflect the laser beams in the main scanning direction, a plurality of laser light outlets (exposure openings) extending in the main scanning direction and allowing the corresponding laser beams to pass therethrough from an interior of the optical scanner toward target surfaces outside the optical scanner, a frame attached in the optical scanner in an area extending between two exposure openings, and a light deflector attached to the frame.
In recent years, in order to enhance the speed of equipment with an optical scanner, such as the printing speed of an image forming apparatus, there have been increasingly employed light deflectors capable of operating at high speeds for scanning with laser beams. However, according to the above-type optical scanner in which a light deflector is attached to a frame in an area between two exposure openings, a resonance may occur at the area of the frame between the two exposure openings due to high-speed operation of the light deflector.
Once such a resonance occurs, the light deflector vibrates. This may disadvantageously cause the optical axes of the laser beams reflected by the light deflector to be out-of-alignment and thus undergo a change in the exposure angle. For this reason, the image forming apparatus equipped with this optical scanner may not correctly expose the surfaces of the photoconductor drums, and as a result, an image may be formed on a sheet with unevenly developed colors.
In view of the above disadvantages, it would be desirable to provide an optical scanner of the type where a light deflector is attached to a frame in an area between two exposure openings, which optical scanner can restrict a resonance during the operation of the light deflector.